This invention relates to a control system of a boiler feed water pump, and more particularly a system of controlling the quantity of water fed to a boiler of a steam electric power generating plant.
As shown in FIG. 1, usually, each unit of a steam electric power generating plant is provided with two steam turbines 50a and 50b for driving feed water pumps 51a and 51b respectively, each designed to feed 50% of the water fed to a boiler under the rated load of a generator 11, and the quantity of feed water is controlled by controlling the speed of these turbines. The steam for driving these feed water turbines is supplied from the main steam pipe 52 through a bypass pipe A and a bleeder pipe B from the main steam turbine 10. However, since each of these steam sources cannot assure sufficient amount of feed water to the boiler under low load conditions of the generating unit or at the time of starting or stopping the same, an independent motor driven feed water pump 53 is installed. Under normal load condition, the flow quantity of the feed water supplied by the pumps 51a, 51b and 53 is controlled by a boiler turbine coordination control device (hereinafter called APC and will be described later), the starting and stopping of these feed water pumps at the time of starting and stopping the generating unit, and the selective starting and stopping of the feed water pumps when the load of the generating unit varies require complicated procedures. Moreover, the dynamic characteristic at the time of starting and stopping varies greatly.
Heretobefore, the starting and stopping of the feed water pumps 51a, 51b and 53 at the time of starting and stopping the generating unit or when the load varies during the normal operation thereof have been controlled by manual operation of an operator or an analogue subloop control system which executes only a portion of various control operations.